Signal receiving apparatus



May 22,, 1934.,

W. D. FESHER L9592 SIGNAL RECEIVING APPARATUS Filed OC'E. 19, 1931 s'rrss PATENT orrics SIGNAL RECEIVING APPARATUS Walter B. Fisher, Norfolk, Mass. Application October 19, 1931, Serial No. 569,779

5 Claims.

This invention relates to circuit arrangements for electron discharge devices generally. More specifically this invention relates to a detector circuit arrangement for radio signal receiving apparatus in which provision is made for counteracting and for neutralizing the effects of pulsations in the currents derived from the sources of current supply employed for energizing the circuits of the different electrodes of the detector.

An object of this invention is to provide an electron discharge device detector employed in a high frequency signal receiving circuit in which an alternating source of current supply is used to energize the filament or cathode electrode, and

a rectified alternating current is used as a source of current supply for the anode circuit, with a capacity coupling between the cathode and the source of anode current supply such that the positive potential impressed upon the capacity coupling is less than the potential applied to the anode electrode of the detector to facilitate in eliminating the effects of the pulsating character of the anode source of current supply upon the circuits associated with the output of the detector.

Another object of this invention is to provide an electron discharge device detector employed in a high frequency signal receiving circuit to energize a plural grid low frequency amplifier adjusted to energize loud-speaker apparatus in which an alternating current supply is employed to energize trodes and a rectified source of source of current the cathode eleccurrent supply is employed to energize the anode circuits, with a potential impressed upon the between the cathode and the supply such that the capacity coupling is greater than the potential applied to the anode electrode of the detector to facilitate the elimination of the effects of the pulsating character of the anode source of current supply upon the circuits energized in accordance with signaling energy transmitted by the detector.

Other and further objects of be apparent to those skilled in the art to this invention will which this invention relates from the following specification and the appended claims. In accordance with this invention the operation of high frequency signal receiving circuits in which the filaments are heated by an alternating source of current supply and the anode circuits are energized by a rectified alternating source of current supply, are by capacitively coupling the tector of the signal receiving greatly improved filament of the deapparatus to the anode source of current supply. This invention the detector is operated as a power detector to energize the input circuit of plural grid lowfrequency amplifiers employing electron discharge devices of the pentode type. In a practical embodiment of this invention it is preferred to use a voltage divider connected across the output of the anode current rectifier and filter. This divider may be connected in such a manner that only a part of the output potential of the rectifier is impressed across it.

A variable connection is provided to the voltage divider for the capacity coupling condenser which is connected to the filament of the detector. The capacity coupling may also be made variable, although this is not essential since sufficient adjustment may be made by the variable connection.

More complete details of this invention may be obtained by reference to the following specification and the accompanying drawing in which the preferred embodiment of this invention is illustrated.

Reference numeral 1 designates an electron discharge device detector having grid, filament and anode electrodes. A resistance 2, having the electrical center thereof connected to the resistance 3 and condenser 4 to ground, that is the signal receiving apparatus metal frame, is connected across the filament of the detector. A low-voltage winding 6 of the transformer 5 is connected to energize the filament directly from the alternating current. Another low-voltage winding 7 is connected to energize the filaments of the pentode type of electron discharge devices 15 and 16 which are connected into a push pull circuit arrangement. A high voltage winding 9 of the transformer 5 is connected to the anodes of the rectifier tube 11. The filament of the rec tifier tube is connected to the low voltage winding 10. The center of the winding 9 is grounded to the metal frame of the power supply apparatus. The transformer 5 is provided with a primary winding 8 which is adapted to be connected to a 110-volt source of alternating current supply.

The center of the winding 10 is connected to the high inductance choke coil 23, the terminals of which are connected to the condensers 24 and 25, which in turn are grounded. One end of the resistance 26 is connected to the choke coil 23 and the other end 260 is connected to the center top of the winding 7. The field winding 22 of the loud speaker 20 is connected to the high potential end of the resistance 26 and also to the ground point 26b. A variable contact 26a is associated with the resistance 26. A connection is provided between this variable contact 26a and a condenser 2a, which is also connected to the resistance 2. This condenser may be variable, or a small variable condenser may be shunted across a fixed condenser to make up the unit 2a.

A high frequency choke coil 12 is connected between the anode of the electron discharge device 1 and the primary of the low frequency transformer 14. A by-pass condenser 13 is provided between the anode of the device 1 and the ground.

The control electrodes of the electron discharge devices 15 and 16 of the pentode type in which an auxiliary grid electrode is connected to the oathode, are connected to the secondary of the transformer 14. The secondary of the transformer 14 is also grounded, preferably at the center. The cathodes of the electron discharge devices 15 and 16 are connected together, either in parallel or in. series, to: the secondary 7 of the transformer 5. The anodes of the devices 15 and 16 are connected to the primary 16 of the output transformer 18. The screen grid electrodes of the: devices 15 and 16 are connected together to the center, or approximate center, of the primary 17 and to the high potential end of the resistance 26. The secondary 19 of the output transformer 18 is connected to energize the movable coil 21 or the loud speaker 20.

In operation, the system of my invention is adjusted so that the hum caused by the use of alternating current for energizing the cathodes of the electron discharge devices directly and by the pulsating character of the currents energizing the anode circuits, is reduced to a mini mum without the use of the heater cathode type of electron discharge device. In the system of this invention the time required to heat the oathodes to operating temperature is reduced to a minimum simultaneously as the hum is substantially eliminated.

The connection 26a from the condenser 2a is made variable so that the hum reducing potential to be impressed from the circuit of the resistance 26 upon the cathode of the detector device 1 may be varied in magnitude until the proper value is obtained. The magnitude of this hum reducing potential is usually less than the anode potential of the detector tube, however, in certain cases where the capacity of the condenser 2a is relatively small it may be desirable to employ a potential higher than the detector anode potential. The capacity of the condenser 2a may also be adjusted simultaneously as the position of the tap 26a is adjusted in order to obtain the optimum adjustment. In order to facilitate adjusting the contact 26a, it is desirable to provide a section in the resistance 26 of relatively low resistance so that the variation in potential will be relatively small as the contact 26a is moved in position along the resistance. This is to simplify the adjustment of the contact 26a.

What I claim and desire to secure by Letters Patent of the United States is:

1. In signal receiving systems the combination of a detector having a filamentary cathode, control electrode and anode, a source of alternating current supply connected to energize said cathode, a source of fluctuating current supply 0011-. nected to said anode and said filamentary cathode, a Voltage divider connected to said source of fluctuating current supply, means for impressing a component of said fluctuating voltage from said voltage divider upon the circuit of said cathode whereby the effect of the fluctuating component of said voltage upon the output circuit of said detector is substantially neutralized, said means comprising a condenser connected between said cathode and said voltage divider.

2. In signal receiving systems the combination of a detector having a filamentary cathode, control electrode and anode, a source of alternating current supply connected to energize said cathode, a source of fluctuating current supply connected to said anode and said filamentary cathode, a voltage divider connected to said source of fluctuating current supply, a condenser connected between said cathode and said voltage divider for impressing a component of said fluctuating voltage from said source upon the circuit of said cathode whereby the efiect of the fluctuating component of said voltage upon the output circuit of said detector is substantially neutralized and means for varying the magnitude of the potential impressed upon said condenser.

3. In signal receiving systems the combinations of a detector having a filamentary cathode, control electrode and anode, a. resistance connected across said filamentary cathode, a source of alternating current supply connected to said cathode, a source of fluctuating current supply connected to said anode and said resistance connected to said cathode, a voltage divider connected across said fluctuating current supply, and means for impressing a fluctuating component of said fluctuating current supply upon the cathode circuit of said detector for substantially neutralizing the effect of the fluctuating character of said current upon the output of said detector, said means including an impedance element connected between said cathode and said voltage divider.

4. In signal receiving means the combination of a detector having a filamentary cathode, a source of alternating current connected to energize said cathode, a resistance connected across said filament, a source of fluctuating voltage connected to a point on said resistance and the anode of said detector, a voltage divider connected across said last mentioned source, and means for passing a fluctuating current through said filamentary cathode from said source of fluctuating voltage for substantially neutralizing hum caused in the output of said detector by said alternating current filament current and said fluctuating voltage anode supply, said means including a capacitive impedance element connected between said filamentary cathode and said voltage divider.

5. In signal receiving means the combination of a detector having a filament, a source of alternating current connected to energize said filament, a resistance connected across said filament, a source of fluctuating voltage connected to a point on said resistance and the anode of said detector, a voltage divider connected across said last mentioned source, and a condenser connected to said filament and said voltage divider for passing a fluctuating current through said filament from said source of fluctuating voltage for substantially neutralizing hum caused in the output of said detector by said alternating current filament current and said fluctuating voltage anode supply and. variable contact means associated with said voltage. divider for varying the effect of said condenser in neutralizing said hum.

WALTER D. FISHER. 

